Van Mounted Camera - Speed Threshold?

[sa_20v]

Hi, my girlfriend encountered a scamera van parked over the A11 this weekend. She was doing a gentle 80mph or less, just wondering if she can expect to receive a ticket, or whether the threshold is set a little higher on dual carriageways?

[puggit]

An indicated 80mph is likely to be more like 75-77mph in real terms (speedos generally over-read). The generally accepted guidelines for the police are 10%+2mph (ie 79 in a 70 limit). However these are guidelines only, and as they are after your cash they might have been zapping people for less then 79mph!

Good luck